This invention relates to particulate inhalers and, in particular, to a mouthpiece for such an inhaler, the mouthpiece being provided with means for ensuring that the particle size of the entrained medicament is minimised.
Mouthpieces for inhalers in the prior art have used many different means for breaking up the particulate medicament which is being inhaled by the patient. Such means include the use of staggered teeth, screens, baffle plates, and filters.
In particular, as disclosed in EP 0237507, it is known to provide one or more deflector devices which are arranged in a stationary configuration within a mouthpiece of the inhaler such that the air flow is accelerated in the region of the deflector devices due to a constriction of the cross section of the mouthpiece. The air flow is caused to accelerate centripetally such that particles or aggregates of the compound are ground into smaller particles by colliding with each other and/or by impacting on the walls of the deflector devices.
A major disadvantage with such an arrangement is that, because the flow area through the mouthpiece is constricted, there is an increase in the inhalation resistance which means that it is more difficult for patients having respiratory diseases to obtain the correct dosage of the medicament.
WO 97/25086 discloses a powder inhalation device which includes a series of baffles past which the air flow with entrained medicament is caused to flow. The flow passes along one surface of each baffle until it contacts a further baffle, causing the air flow to change flow direction within a delivery conduit. Such changes in flow direction reduce the flow rate of the medicament and increases the inhalation resistance.